1. Field of the Invention
The present invention relates to an integrated compressed gas fuel storage system for motor vehicles, called the Integrated Storage System (ISS), comprising a plurality of high pressure gas storage cylinders (hereinafter referred to as pressure cells), interconnected by a gas control assembly incorporating operational and safety controls all contained within a molded housing.
2. Background
Domestic oil production is declining due to U.S. oil reserves becoming more difficult to tap while demands on petroleum production escalate. Half of the U.S. oil supply is imported and the U.S. Department of Energy predicts a 60 percent deficiency by the year 2010. International oil companies relying on easily extracted foreign oil may meet the demand but at an unacceptable cost to the U.S. economy. The primary cause of the short fall is the motor vehicle. Current predictions indicate motor vehicles will proliferate globally from 500 million today to one billion by the year 2030. The solution is obvious, alternative fuels must be developed for motor vehicles.
It has been demonstrated that compressed gasses such as hydrogen, propane, methane or natural gas are viable alternatives to petroleum as a fuel source for motor vehicles. Natural gas is one of the more interesting of the alternatives because it is a plentiful commodity in the United States and therefor inexpensive. As a result, more than 30,000 natural gas vehicles are currently in use in the United States. These vehicles have demonstrated low fuel costs and reduced engine maintenance while affording a significant reduction in exhaust emissions. Such vehicles have been restricted to fleet trucks, delivery vans, buses and taxis due to their limited range. The restrictions and limitations are caused by the space required for existing compressed gas fuel systems. This space penalty results in lost truck bed volume, automobile trunk volume and range. Furthermore, higher initial purchase prices are experienced due to the cost of the gas storage systems.
Compressed gas vehicle fuel systems traditionally consist of a single large cylinder or a series of smaller cylinders mechanically clamped together and rigidly mounted to the vehicle chassis. Numerous clamps, brackets, and redundant valves and safety devices are required to comply with federal law. Installation and maintenance costs are high.
An example of a contemporary compressed natural gas fuel system for an automobile is illustrated in FIG. 1. In this typical system, compressed natural gas storage cylinders reside in the trunk, taking up valuable cargo space, and numerous safety devices are redundantly incorporated throughout the fuel delivery system to insure that each tank has adequate safeguards to meet the applicable regulations. The size and/or number of tanks can be reduced, but this solution results in an unacceptable range limitation. The foregoing and related factors have hampered sales of light-duty natural gas powered vehicles and development of the industry.
The present invention utilizes the latest developments in materials and manufacturing processes to produce a compressed gas fuel storage system that avoids the limitations of current gas storage systems discussed above. The materials and processes used enable mass production of the fuel storage system, significantly reducing its initial cost. Of critical importance, the invention includes the design of a lightweight, high strength storage system that meets or exceeds the safety requirements and application standards dictated by applicable governmental and industrial standards.
The compressed gas fuel storage system of the invention includes a plurality of composite over-wrapped cylinders (pressure cells), a unitizing, high strength outer shell with internal protective material (i.e. foam or honeycomb) for the pressure cells, a central gas control assembly with interconnecting gas lines, a sealed, but removable for service, protective cover for the gas control assembly, and straps to secure the system to the vehicle.
The outer shell is an unstressed (un-pressurized), fire-resistant structure that serves the purpose of unitizing the plurality of pressure cells into a single container capable of withstanding physical abuse associated with motor vehicle applications. The outer shell and impact-absorbing material (i.e. foam or honeycomb) contained therein serve to protect the pressure cells from impact loads. The gas control assembly protective cover and impact-absorbing material such as, but not limited to, foam or honeycomb contained therein serving to protect the gas control assembly from impact loads. The outer shell and the gas control assembly protective cover are fabricated from an impact-resistant, fiber-reinforced thermoplastic or thermoset plastic material. The outer shell, in conjunction with elastomeric gaskets and grommets, also serves to protect the pressure cells from exposure to water, road salt, automotive fluids (i.e. gasoline, motor oil, battery acid, antifreeze, brake fluid, etc.), and sunlight.
Only a single gas control assembly is needed to meet all safety standards because the plurality of pressure cells has been unitized into a single container. This gas control assembly includes a thermally activated pressure relief device, a manual service shut-off valve, an electric solenoid valve, and a port to connect the fuel storage system to the vehicle engine and the refueling adapter.
The compressed gas fuel storage system of the invention is designed to be attached to the vehicle with straps, tabs, or brackets which do not alter the structural compliance of the vehicle chassis in the event of a rear end collision. This is critical in light-duty vehicles which are designed to protect the passengers by absorbing collision energy through deformation of the chassis in non-passenger compartment regions of the vehicle (i.e. trunk and engine compartment regions).
Therefore, it is a primary objective of the present invention to provide a compressed gas fuel storage system for vehicles that is shaped in a near-rectangular or other non-cylindrical configuration to accommodate available chassis space and vehicle packaging constraints.
Another objective of the invention is to provide a compressed gas vehicle fuel storage system utilizing a single gas control assembly, including a thermally activated pressure relief device, a manual service shut-off valve, an electric solenoid valve, a port to connect the fuel system to a vehicle engine and refueling adapter, and a plurality of pressure cells contained within a molded housing.
A further objective of the present invention is to provide a compressed gas vehicle fuel storage system, which incorporates cylindrical pressure cells with near-hemispherical shaped domed ends.
A further objective of the present invention is to provide a compressed gas vehicle fuel storage system incorporating a plurality of pressure cells contained within a molded housing incorporating strengthening webs strategically placed between the pressure cells.
A still further objective of the invention is to provide a molded container for a plurality of pressure cells which is assembled by snap lock or other means holding individually molded container segments together.
Another objective of the invention is to provide a molded gas control assembly protective cover for a compressed gas vehicle fuel system.
A further objective of the invention is to provide means to maintain ambient atmospheric pressure within a molded container which functions as a protective housing for a plurality of pressure cells.
A still further objective of the present invention is to provide mounting means for a plurality of pressure cells within a protective container that allows expansion and contraction of the fuel cells during the course of normal pressurization and depressurization operations without stressing the container.
A still further objective of the present invention is to provide means for isolating individual ones of a plurality of pressure cells within a protective container to enable said container to undergo penetration with a high-speed projectile without causing catastrophic rupture of the container, but allowing the gas to vent in a controlled manner. A still further objective of the present invention is to provide a means of attaching a compressed gas vehicle fuel storage system to a vehicle by means of straps, tabs, or brackets for keeping said system fixed to the chassis under normal driving conditions but allowing the system to be displaced relative to the chassis in the event of a chassis crushing, high-speed collision.
Another primary objective of the present invention is to provide a compressed gas vehicle fuel storage system, which meets or exceeds government and industrial standards.
An objective of the present invention is to provide a compressed gas vehicle fuel storage system which meets or exceeds the standards developed by the National Fire Protection Association for compressed natural gas vehicle fuel systems as published in ANSI/NFPA 52, Compressed Natural Gas (CNG) Vehicular Fuel Systems, 1995, published by the American National Standards Institute and National Fire Protection Association and incorporated herein by reference.
Another objective of the invention is to provide a compressed gas vehicle fuel storage system which meets or exceeds the standards and revisions thereto developed by the Natural Gas Vehicle Coalition and published in the American National Standard for Basic Requirements for Compressed Natural Gas Vehicle (NGV) Fuel Containers, ANSI/IAS NGV2-1998, and incorporated herein by reference.
A still further objective of the invention is to provide a compressed gas vehicle fuel storage system which meets or exceeds the standards and revisions thereto developed by the Natural Gas Vehicle Coalition and published in the American National Standard for Pressure Relief Devices for Natural Gas Vehicle (NGV) Fuel Containers, ANSI/IAS PRD 1-1998., and incorporated herein by reference.
Another objective of the present invention is to provide a compressed gas vehicle fuel storage system which meets or exceeds the standards developed by the National Highway Traffic Safety Administration (NHTSA) of the Department of Transportation (DOT) and published by the National Highway Traffic Safety Administration as Federal Motor Vehicles Safety Standard, Standard No. 303, Fuel System Integrity of Compressed Natural Gas Vehicles, 1994, and incorporated herein by reference.
A further objective of the present invention is to provide a compressed gas vehicle fuel storage system which meets or exceeds the standards developed by the National Highway Traffic Safety Administration (NHTSA) of the Department of Transportation (DOT) and published by the National Highway Traffic Safety Administration as Federal Motor Vehicles Safety Standard, Standard 304, Compressed Natural Gas Fuel Containers.